Increased demand on the electric distribution grid increases the need for more careful management of system voltage, especially with regards to peak demand. Over a 24 hour period, the peak power consumed may be much higher than the average power. Since transformers, wire, and other infrastructure may be sized for the highest power, not the average power, increases in peak demand require equipment capable of handling that peak demand, such as larger transformers and so on. Conversely, reducing the peak demand allows utilities to postpone the upsizing of infrastructure in the face of rising total demand. Utilities may purchase power at much higher rates during times of peak demand, due to typical contract agreements. Reducing power consumption during times of peak demand may have larger financial benefit than reducing consumption at other times. Flattening the demand curve may have multiple benefits for utilities, and may reduce the need for extra generation as loading increases.
One technique for reducing demand is Conservation Voltage Regulation (CVR). With CVR, the distribution system voltage is reduced during times of peak demand. Resistive loads may consume less power when the voltage is reduced. Power consumption may be proportional to the square of the voltage for many loads, so a 1% reduction in voltage can produce a larger than 1% change in power consumption. Reductions of between 2% and 10% of total power have been achieved with CVR techniques.
To implement CVR, utilities may need much finer control over the distribution system voltage, and the voltage delivered to customers. To accomplish this, devices may be required both to adjust and measure the distribution line voltage at many strategic locations. Voltage measurements may be required for two reasons. First, actual voltage levels may be needed as part of a closed-loop feedback system, so a centralized Demand Management System can make decisions about how to adjust voltage regulators and other management devices. These voltage readings may typically be used in conjunction with system models and historical patterns, and after suitable calculations, commands may be sent to voltage regulators, capacitor banks, and so on. Second, voltage measurements may be needed to insure that regulatory voltage limits are not crossed. For example, as part of a CVR system, the voltage is typically lowered during times of peak demand, leaving much less safety margin. Regulatory limits dictate how low a voltage is allowed, and monitoring may be required to insure that these limits are met. These limits are applied at the point of delivery to customers, which may typically be the service entrance or revenue meter location.
Traditional sensors may be too slow for real-time systems, for example, those based on slow power line carrier systems, or many Automated Meter Reading (AMR) systems, or too bulky and expensive for widespread or residential deployment. Existing cellular radio solutions may not be practical for use in residential locations, due to the size and obtrusiveness of the hardware. In addition, existing systems have limited, or no, provision for storing and analyzing historical voltage data.